Hubbard Brook Experimental Forest

Hubbard Brook Experimental Forest is a wooded area in New Hampshire’s White Mountains that is used as a living ecology laboratory. Established in the 1950s by the US Forest Service, it was initially used to study best practices in forestry. Within a short time, however, scientists realized that the 8,700-acre site would be ideal to study the forest ecosystem and the impact events in one part of the country or world can have on ecosystems in another area. The significance of acid rain was uncovered there, and the site became the home of the Hubbard Brook Ecosystem Study. This initiative brings together scientists from throughout the world to study the effect of environmental factors on plant and animal life; the effects of acid rain and other water-borne chemicals on an ecosystem; and hydrology, or how water from precipitation and other sources moves through an ecosystem.

Background

The Hubbard Brook Experimental Forest originated in 1955. The US Forest Service chose the wooded site located in the New Hampshire towns of Woodstock, Ellsworth, and Thornton to conduct research on precipitation, stream flow, and other water issues affecting a forest’s health. While the area was similar to many others around it, the Hubbard Brook site had a few features that made it ideal for the forest service’s research. It was in a valley that was shaped like a bowl, had vegetation and geology that was consistent throughout the area, and had a riverbed that retained water well. These factors all made it well suited for obtaining accurate information about the area’s water flow.

This was important because scientists believed that they could learn about the overall health of the forest by studying the water running through it. Much like a medical doctor tests urine to determine how well the body is processing food and waste, forestry scientists believed they could test a forest’s water to see how healthy the forest was. In the space of a few years, scientists realized that they could learn much more from studying the water and other aspects of the Hubbard Brook area, and the Hubbard Brook Ecosystem Study began.

Overview

The Hubbard Brook Experimental Forest is a hilly, 8,700-acre wooded area in the southwestern portion of the White Mountain National Forest in central New Hampshire. The elevation is between 730 and 3,300 feet (222 and 1,015 meters). The region experiences four seasons, and about one-third to one-quarter of the 1,400 millimeters (55 inches) of precipitation it receives annually falls as snow. Average temperatures range from 16 degrees Fahrenheit (-9 degrees Celsius) in January to about 64 degrees Fahrenheit (18 degrees Celsius) in July.

The sandy, loamy soil of the area supports a strong second-growth forest, which is a forest that grows in place of one that has been cut down for agriculture or lumbering. The forest’s newer growth is consistent in its level of maturity. The make-up of the forest is about 80 percent northern hardwoods, such as sugar maples, and 10 to 20 percent spruces and firs, such as the red spruce, along with some softwood trees, such as hemlocks.

Hubbard Brook has numerous small watersheds, or areas of land, that separate water that is flowing to different rivers, streams, or other bodies of water. Nine of these have been outfitted with stream gauging stations. These contain equipment that enables scientists to measure how water flows, what chemicals and sediment are in that water, and how it moves through the ecosystem.

The experimental site also includes several streams. Some of these are relatively small headwater streams that feed into larger streams and rivers. Hubbard Brook, the site’s namesake, runs into the Pemigewasset River that is just outside the experimental forest. Also nearby but outside the Hubbard Brook site is Mirror Lake. Some scientists working with the Hubbard Brook Ecosystem Study include Mirror Lake in their research.

As an outdoor site subjected to the elements, Hubbard Brook Experimental Forest has experienced its share of natural events that have impacted the forest. Ice storms, microbursts, heavy winds, pests and diseases, and changes in precipitation levels have all left their mark. The forest has also felt the effect of human-made challenges over the years, which have included deforestation and acid rain, or rainfall contaminated with pollution, typically from acidic gases produced when coal and gasoline are burned.

Hubbard Brook Experimental Forest played a key role in research about acid rain and efforts to reduce pollution. In the summer of 1963 (around the time the experimental forest became part of the ecosystem study project), a sample that scientists collected there helped them understand the effects of acid rain. This led to legislation and other changes to protect air quality.

The sample was collected by a researcher working with ecologist Gene Likens (1935– ), who co-founded the Hubbard Brook Ecosystem Study along with Herb Bormann (1922–2012). When they studied the sample, they discovered that it contained one hundred times more acid than they had expected. Expanded study in other areas led to the conclusion that coal and oil being burned hundreds of miles away in the Midwest was releasing nitrogen oxide and sulfur dioxide into the atmosphere. These chemicals combined with the water in the atmosphere to form acid and were carried in clouds before dropping back to Earth in the form of acid rain. Likens and Bormann published their findings in the magazine Science. This led to legislative action, such as the Clean Air Act of 1990.

Researchers continue to study the trees and plants in the forest to determine how they are affected by factors from natural and human origins. In addition to helping bring about changes in air quality, the work performed at Hubbard Brook Experimental Forest has improved water quality as well as the health of animal and insect life. It has also changed forestry practices and inspired new forest management programs, such as limiting the practice of clear-cutting, or removing all trees in an area.

Bibliography

“About the Forest.” Hubbard Forest Ecosystem Study, hubbardbrook.org/about-the-forest/. Accessed 11 Aug. 2022.

Franz, Julia. “One of the largest ‘test tubes’ in science is an 8,000-acre forest in New Hampshire.” The World, 9 Oct. 2016, theworld.org/stories/2016-10-09/one-largest-test-tubes-science-8000-acre-forest-new-hampshire. Accessed 11 Aug. 2022.

“Gene E. Likens.” The Franklin Institute Awards, www.fi.edu/laureates/gene-e-likens. Accessed 11 Aug. 2022.

“Hubbard Brook.” Cornell University Audubon, www.birds.cornell.edu/hubbardbrook/hubbard-brook/. Accessed 11 Aug. 2022.

“Hubbard Brook Ecosystem Study.” Cary Institute of Ecosystem Study, www.caryinstitute.org/science/research-projects/hubbard-brook-ecosystem-study. Accessed 11 Aug. 2022.

“Hubbard Brook Experimental Forest.” United States Department of Agriculture Forest Service, www.nrs.fs.fed.us/ef/locations/nh/hubbard-brook/. Accessed 11 Aug. 2022.

Likens, Gene E. “The Hubbard Brook Ecosystem Study: Celebrating 50 Years.” Ecological Society of America Bulletin, 1 Oct. 2013, esajournals.onlinelibrary.wiley.com/doi/full/10.1890/0012-9623-94.4.336. Accessed 11 Aug. 2022.

MacLaughlin, Nina. "Brook Experimental Forest in North Woodstock, New Hampshire." Yankee Magazine, New England.com, 3 Sept. 2023, newengland.com/travel/new-england/these-trees-say-so-much-hubbard-brook-experimental-forest-in-north-woodstock-new-hampshire/. Accessed 8 Nov. 2024.

Ropeik, Annie. “Pandemic Sparks Innovation at N.H.’s Influential Hubbard Brook Experimental Forest.” WBUR Public Radio,8 Feb. 2021, www.wbur.org/news/2021/02/08/pandemic-innovation-nh-hubbard-brook-experimental-forest. Accessed 11 Aug. 2022.